The invention relates to a method of securing electronic components, in particular large-area power semiconductors, to a substrate by pressure sintering. In the conventional production of large-area power semiconductors, such as thyristors and the like, first a substrate formed of molybdenum, a wafer formed of aluminum, and a semiconductor body formed of silicon are joined to one another by heating to approximately 700.degree.-800.degree. C. The connection between the aluminum and the molybdenum can be considered as a type of solder connection, whereas the connection between the aluminum and silicon is achieved by the formation of a eutectic alloy. A simultaneous doping of the silicon takes place during this alloying process. Due to the different heat expansion coefficients of the individual components, the high temperature stress leads to high levels of tension in the power semiconductor, which is manifest in the finished product in the form of corresponding curvatures.
In so-called MOS-technology, during doping and in the formation of the structures, levels of accuracy in the .mu.m range are facilitated by the use of photo-resist techniques and etching techniques. However, it has not previously been possible to apply MOS-technology to the production of large-area power semiconductors since the high temperatures required for alloying on to a substrate would lead to the destruction of the pn-junctions and of the fine aluminum structures. Neither would it be possible to form the structures following the alloying of the silicon onto the substrate as the existing curvatures would rule out the use of photo-resistant techniques and etching techniques with accuracy levels in the .mu.m range.
German OS No. 3 414 065, incorporated herein, has already disclosed a method of securing electronic components on a substrate by the use of pressure sintering in which
a paste formed of metal powder, preferably silver powder, and a solvent is applied in the form of layers to the contacting layer of the component and/or the contact surface of the substrate; PA1 the component is then placed onto the substrate; PA1 the solvent is completely expelled; and PA1 the entire arrangement is then heated to sintering temperatures of between 380.degree. and 420.degree. C., with the simultaneous application of a mechanical pressure of 80-90 N/cm.sup.2. PA1 a. a paste comprised of metal powder and a solvent is applied in the form of layers to the contacting layer of the component and/or the contact surface of the substrate; PA1 b. the applied paste is then dried; PA1 c. the component is placed onto the substrate; and PA1 d. the entire arrangement is then heated to the sintering temperature, while simultaneously applying a mechanical pressure of at least 900 N/cm.sup.2.
The use of this known method has permitted small electronic components to be joined to a substrate at a relatively low level of thermal stress and with a high level of mechanical stability. The connecting layers formed by the pressure sintering exhibit extremely small electrical contact resistances and also very small thermal resistances. However, the application of this known method to the securing of large-area power semiconductors to a substrate did not lead to utilizable results. The connecting layers formed by the pressure sintering were always in homogeneous and permeated by channel-like structures which thus resulted in low levels of bonding stability, high electrical contact resistances, and high thermal resistances.